5 messages · oryie, Paul Smith, rafamoral +1 more
Hello! I want to use R to calculate the variable x which is in some eqation, give an example: 3*x-log(x)+1=0, how to solve equation to get the exact x in R? Thank you very much!
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I want to use R to calculate the variable x which is in some eqation, give an example: 3*x-log(x)+1=0, how to solve equation to get the exact x in R?
You could use uniroot(), but your equation has no real solution. Paul
If you are looking for a solution to a polynomial equation with imaginary solutions you could use polyroot(). Example: To solve the equation: 1 + x + x^3 + 2*x^4 = 0 you create a vector with the coefficients of x and use polyroot: z <- matrix(c(1,1,0,1,2), ncol=1) polyroot(z) Also try ?polyroot Rafael
On Sat, Feb 7, 2009 at 10:20 AM, oryie <43248523 at qq.com> wrote:
I want to use R to calculate the variable x which is in some eqation, give an example: 3*x-log(x)+1=0, how to solve equation to get the exact x in R?
You could use uniroot(), but your equation has no real solution. Paul
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
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As suggested by somebody else, uniroot() can be used to solve equations in one unknown variable. However, you will never get the "exact x" in R, only an approximate root... Best, Giovanni
Date: Sat, 07 Feb 2009 02:20:10 -0800 (PST) From: oryie <43248523 at qq.com> Sender: r-help-bounces at r-project.org Precedence: list Hello! I want to use R to calculate the variable x which is in some eqation, give an example: 3*x-log(x)+1=0, how to solve equation to get the exact x in R? Thank you very much! -- View this message in context: http://www.nabble.com/R-solve-equation-tp21886831p21886831.html Sent from the R help mailing list archive at Nabble.com.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Giovanni Petris <GPetris at uark.edu> Associate Professor Department of Mathematical Sciences University of Arkansas - Fayetteville, AR 72701 Ph: (479) 575-6324, 575-8630 (fax) http://definetti.uark.edu/~gpetris/
As suggested by somebody else, uniroot() can be used to solve equations in one unknown variable. However, you will never get the "exact x" in R, only an approximate root... Best, Giovanni
Date: Sat, 07 Feb 2009 02:20:10 -0800 (PST) From: oryie <43248523 at qq.com> Sender: r-help-bounces at r-project.org Precedence: list Hello! I want to use R to calculate the variable x which is in some eqation, give an example: 3*x-log(x)+1=0, how to solve equation to get the exact x in R?
That is correct, Giovanni. But the given equation has no (real) solution. Paul